A. Field of the Invention
The present invention relates to ski poles, more particularly to shock absorbing ski poles, and to a method of adjusting the length of ski poles having shock absorbing devices therein.
B. Brief Description of the Prior Art
A number of skiing maneuvers are executed by the skier planting the ski poles in the snow and pressing downwardly on the poles to support at least part of the skier's weight from the poles. In some instances, the poles are shoved quite abruptly into hard snow, with substantial impact being transmitted through the poles to the skier's hands, arms and shoulders.
Since some of these manuevers are performed rather rapidly, the ski poles should have a proper "feel" for the skier, and they should be easily movable to various positions. Accordingly, in the design of ski poles, careful attention is given to such details as the configuration and weight distribution in the ski poles, the arrangement of the hand grips to give proper control, etc. Thus, while it is desirable to make ski poles quite lightweight and easily maneuverable, it is also desirable that the ski poles give the user the "feel" of firmness and proper support.
There have been attempts in the prior art to provide ski poles with shock absorbing mechanisms to ease the impact transmitted through the poles to the skier. One such device is shown in German Patent No. 2,055,597, where the hand grip for the ski pole is mounted for up and down motion on the upper end of the ski pole. A spring is provided to urge the hand grip to its upper position and thus resist downward movement of the hand grip relative to the pole. A similar device is shown in Swedish Patent No. 132,429. While such devices have some capability in cushioning impacts imparted from the ski pole through the hand grip, there is the problem that the rebound action of the spring produces an undesired effect in the "feel" of the ski pole. Further, in at least some of the prior art devices of this type, there is not the necessary firmness between the hand grip and the pole to give the user the proper feeling of control when the skier is manipulating the ski pole from one position to another.
There have been other attempts to place spring-like mechanisms in the tip end of the pole, such devices being shown in U.S. Pat. No. 3,797,845, Kepka et al, and in U.S. Pat. No. 3,637,229, Klemm. One of the problems with such devices lies in the fact that the tip of the ski pole should be made as light-weight as possible, to enable the skier to rapidly swing the tip of the ski pole from one location to another. Not only do such spring-like devices in the tip of the ski pole add undesired weight, but such mechanisms are at a location in the ski pole where they are subjected to substantial torsion loads. Thus, the mechanism would be more likely to malfunction, and if it were made stronger to avoid such possible malfunctions, even more weight would be added to the tip of the ski pole.
Also, various spring-like cushioning devices are noted in areas other than the ski art, one such area being that of crutches used by people having leg injuries. Since the requirements of provided an effective ski pole are substantially different than those relating to crutches, that art is not considered by the applicants to be closely analogous. However, it is cited herein to fulfill the requirement that all prior art of possible relevance be noted. One such device is shown in U.S. Pat. No. 2,478,667, Shellhouse et al, where there is a crutch having a lower tip end slide mounted in a cylinder. Upward movement of the tip end into the cylinder is resisted by a pneumatic piston and cylinder arrangement, and by a compression spring positioned in the pneumatic chamber between the piston and the end of the cylinder wall. There is in the end wall of the cylinder a check valve which permits outflow of air from the chamber defined by the cylinder, but which resists an inflow of air. Thus, the downward movement of the tip in response to the compression spring expanding is resisted to some extent by lower air pressure in the chamber. There is a second valve which also communicates to the cylinder chamber to control the inflow of air to the chamber. A somewhat similar arrangement is shown in U.S. Pat. No. 3,486,515, Chrysostomides.
To return to a discussion of the prior art relating to ski poles, while there have been previous attempts to incorporate shock absorbing devices into ski poles, to the best knowledge of the applicants herein, none of these have proven to be commercially successful or used to any substantial extent by skiers. It is believed that one of the main reasons for this is that at least some of such prior art devices have suffered what might be called a "pogo stick" effect, in that the ski poles are somewhat "bouncy". While this springiness obviously gives the effect of absorbing impact, it also gives the skier a lack of a feeling of firmness and precision in making his pole plants.
Also, quite likely certain technical problems have contributed for the failure of the prior art to deal with this problem successfully. As indicated earlier, to place such shock absorbing devices at the tip end of the pole adds undesired weight at the place where it is least desired, and also locates the shock absorbing device in an area where it is more likely to encounter damaging torsion loads. On the other hand, placing the device in the upper gripping end of the ski pole proposes a different set of problems. First, the size of the hand grip is necessarily limited, since it must fit comfortably into the hand of the skier, and this necessarily places certain constraints on the sort of mechanism which can be sized to be placed in this area. Secondly, the "feel" in the area of the hand grip is particularly critical. The hand grip must firmly engage the pole in such a manner that there is no "play" in the handle of the pole. In one sense, there are what might be called contradicting requirements in providing an effective shock absorbing ski pole. First, there must be a certain amount of "give" or cushioning, to dissipate the effect of impact transmitted through the pole. On the other hand, the "feel" of the pole should be such that the skier senses complete firmness and control in manipulating the pole, planting it for a manuever, and withdrawing it for a subsequent maneuver.
Another consideration is the maintenance and adjustment of the ski poles. For reasons of economy, ski shops prefer not to handle ski poles in a great variety of lengths, simply to keep the inventory to a practical minimum. On the other hand, skiers quite often want precise adjustments in the length of the ski pole. Therefore, it is a common practice in ski shops to adjust the length of a conventional ski pole simply by removing the hand grip from the ski pole, sawing off the desired amount from the upper end of the pole and then replacing the hand grip. Thus, any attempt to provide a ski pole with a shock absorbing device should be compatable with the capability of easy adjustment in the length of the ski pole.
In view of the foregoing, it is an object of the present invention to provide a shock absorbing ski pole which provides a desirable balance of features such as those considered above. More specifically, it is an object to provide a ski pole which effectively absorbs shock impacts transmitted through the pole, provides a proper "feel" of firmness and control for the skier, and yet provides ready adjustment of length in the ski pole.